Impact of restoration thickness and tooth shade background on the translucency of zirconia laminate veneers: An in vitro comparative study

Purpose

Our in vitro comparative study aimed to investigate the impact of thickness and tooth shade background on the translucency of highly translucent zirconia veneers.

Materials and Methods

A total of 75 5Y-TZP zirconia veneers of shade A1 were fabricated with thicknesses of 0.50 mm (n = 25), 0.75 mm (n = 25), and 1.0 mm (n = 25). The translucencies were measured on composite resin teeth with shades A1, A2, A3, A3.5, and A4 using a digital color imaging spectrophotometer. Data were analyzed using ANOVA and post hoc Tukey's test (p < 0.05).

Results

The translucency values were optimal for the veneers placed over the substrate teeth with shades A1 and A2, regardless of the veneer thickness. Additionally, veneers with a thickness of 0.50 mm exhibited significantly higher translucency than those with thicknesses of 0.75 mm and 1.0 mm.

Conclusions

Our study demonstrated that the translucency of the highly translucent zirconia veneers was influenced by both veneer thickness and tooth shade background. The optimal veneer thickness for achieving the highest translucency was 0.50 for the veneers with A1 and A2 shades placed over the substrate teeth.

Clinical Relevance

The optimal thickness for achieving the highest translucency of the highly translucent zirconia laminate veneers was 0.50 mm for the veneers with A1 and A2 shades placed over the substrate teeth. Clinicians and dental technicians could consider this when selecting materials for aesthetic restorations.

Investigation of the esthetic perception of different canine parameters

OBJECTIVES

The aim of this study is to analyze the esthetic perception of selected canine features, namely crown length, shade, inclination, and angle of incisal edge tip.

MATERIALS AND METHODS

The anterior maxillary teeth of a Central European woman were photographed and digitally modified in order to investigate esthetic perceptions of the above four categories. Three groups of examiners with different levels of experience in the field of dentistry (laypersons/inexperienced dental students, advanced dental students, dentists) evaluated the photographs twice with the help of visual analogue scales.

RESULTS

The best-evaluated canines have approximately the same length as the central incisor, have the same shade as the other anterior teeth, are best embedded in a lighter overall tooth shade, are neutral to slightly palatal inclined, and have a right angled to rounded incisal edge (≥ 90°). The canines evaluated as least esthetic, however, are longer than the central incisors, darker, inclined labially, and have a tapered incisal edge. No significant differences could be found between the evaluations of the groups with regard to the four feature categories.

CONCLUSIONS

Laypersons, advanced dental students, and dentists generally evaluate according to the same esthetic standards. Gender does not have a significant influence on evaluation. Clear definitions of esthetically favored shades, incisal edge shapes, inclination, and lengths of the canines can be given.

CLINICAL RELEVANCE

Since the esthetics of the smile line play a critical role for patients, dentists, dental technicians, and their supplying industry, knowledge of the esthetically preferred morphology of canines is essential.

CLINICAL SIGNIFICANCE

The aim of this study is to give clear definitions of esthetically favored shades, incisal edge shapes, and lengths of the canines, as the esthetics of the smile line play a critical role for patients, dentists, dental technicians, and their supplying industry (e.g., denture tooth manufacturers). Precise knowledge of esthetic preferences is important in clinical practice for both dentists and dental technicians, for example, in order to adequately advise patients regarding esthetic corrections. Also, in the case of missing teeth, this knowledge is essential for optimal and satisfactory restorations. Thus, this study can contribute to the satisfaction of general practitioners and patients.

Use of a new skin colour measurement method for the investigation of relationship between skin and tooth colour

Purpose

There is conflicting information about the relationship between tooth color and skin color in the literature. The aim of the present study was evaluation of the correlation between L, a, b values of skin and tooth shade using a new skin color measurement method.

Materials and methods

CIELab values of teeth were obtained through measurements from the middle third of the labial surfaces on central incisors of individuals using a clinical spectrophotometer. CIELab values of the skin were measured through facial images using a software which was manufactured for present study. A statistical analysis program (SAS 9.4) was used for the analysis of the data. Kolmogorov-Smirnow test, t-test, and multivariate regression analysis were used to evaluate the data (α=0.05).

Results

Correlations between variables revealed that while the lowest and statistically insignificant correlations were observed with a* values of the skin, significant correlations did not exceed moderate level (p < .05). When considering regression analysis results, b* values of the skin had a statistically significant effect in describing b* values of the tooth, while L* and a* values of the skin were observed to be insufficient in describing L* and a* values of the teeth.

Conclusion

Results of this study suggest that different significant correlations were observed between the skin and tooth color for different L*, a*, and b parameters (p <0.05 and p <0.01). The results indicated that skin color can be used for tooth color selection in case of loss of natural teeth or when discoloration is present on existing teeth.

Effect of application of desensitizers before bleaching on change of tooth shade

The aim of this in vitro study was to evaluate the effects of desensitizer pre-treatment on in-office bleaching using an artificial discoloration tooth model. The stained specimens were divided into four groups (n=10); without application (Control group), Shield Force plus (SF group), UltraEz (UE group) and Teeth Mate AP paste (TM group) applied before bleaching. Each group was bleached by an in-office bleaching agent. The CIE L*a*b* values were measured by a colorimeter before and after ten consecutive bleaching treatments and the color difference (∆E) was calculated. There was no statistical difference among ∆E values of Control, UE, and TM groups (p>0.05). There was a significant difference between SF and Control groups (p<0.001). It was concluded that application of TM and UE did not affect the change of tooth shade while SF application impeded the bleaching effect.

The Effect of Accelerated Aging on the Colour Stability of Composite Resin Luting Cements using Different Bonding Techniques

INTRODUCTION

The main criterion of successful aesthetic restoration is to match the colour of the adjacent teeth. Porcelain laminate veneer is widely practiced indirect restoration in the contemporary aesthetic dentistry. The underlying luting cement colour influences the final outcome of the thin, translucent veneer shade. Hence, colour stability of luting cement is important criteria during their selection.

AIM

The objective of the study was to assess the colour stability of the different dentin bonding techniques in composite resin luting cements.

MATERIALS AND METHODS

A total of forty intact, non carious teeth were prepared to receive Porcelain Laminate Veneers (PLV). The lithium disilicate PLV were fabricated, and fitting surface was conditioned with 5% hydrofluoric acid and silane application. According to the bonding technique employed for the cementation of the PLV, the teeth samples were randomly divided into the four groups of ten each. The Group I and Group II samples were conditioned with etch and wash; the polymerization of resin was accomplished with the dual cure for Group I and light cure for Group II. The Group III and Group IV samples were conditioned with self-etch and self-adhesive technique correspondingly. The teeth shade was recorded in similar locations with a spectrophotometer before and after subjecting them to the accelerated ageing process. The ageing process included the thermocycling process in water between 5°C and 55°C for 5000 cycles followed by 100 hours xenon light exposure. The data were analysed with SPSS 19.0 by ANOVA and LSD post-hoc comparison.

RESULTS

The higher mean colour change was observed in Group I sample (etch washdual cure) with a ∆E value of 2.491. The ∆E value for Group II (etch wash-light cure) and Group III (selfetch) was 1.110 and 2.357 respectively. The lowest mean colour change was observed in Group IV (self-adhesive) with ∆E at 0.614. Statistical analysis showed significant differences between Group IV and Group I; Group IV and Group III with p<0.05.

CONCLUSION

The self-adhesive and etch-wash light cure luting cements were found to be less susceptible for colour changes due to accelerated ageing.

Effects of combining ozone and hydrogren peroxide on tooth bleaching: A clinical study

OBJECTIVES

The purpose of this study was to evaluate the efficiency of bleaching after combining ozone and 38% H2O2 in comparison to the sole use of 38% H2O2.

METHODS

Consecutive 26 participants (13 males and 13 females) were recruited into this study. They were randomly allocated into 2 groups (n=13 for each group). In group 1 (test group); the participants' upper anterior teeth were treated with 38% H2O2 for 20min then the teeth were exposed to ozone for 60s (healOzone(®) X4, KaVo Dental, Biberach, Germany). In group 2 (controls); the upper anterior teeth were treated with 20min of 38% H2O2 only. The shade of teeth was evaluated by recording the L* a* b* values and Vita Classic shades at study baseline and after bleaching in both groups. The statistically significant changes were set at P≤0.05.

RESULTS

Tooth sensitivity and teeth shades were comparable between groups at study baseline (p>0.05). Controls reported more tooth sensitivity following bleaching (p<0.001). Teeth achieved better Vita shades, higher L* values (lighter shades), and lower a* and b* values (lighter shades) after bleaching in both groups (P≤0.05). However, teeth bleached with H2O2 and ozone achieved better Vita shades, higher L* values and lower a* values (lighter shades) than those bleached with H2O2 alone (p<0.001). Changes in b* values were not significantly different between groups.

CONCLUSIONS

Bleaching with 38% H2O2 for 20min followed by 60s of ozone application would result in teeth with lighter shades than bleaching with 38% H2O2 alone.

Improved tooth bleaching combining ozone and hydrogen peroxide--A blinded study

OBJECTIVES

To evaluate the efficacy of tooth bleaching using ozone after hydrogen peroxide (H2O2) in comparison to the use of H2O2 alone.

METHODS

70 extracted teeth were randomly distributed into two groups. Teeth surfaces in group 1 (n=35) were treated using 38% H2O2 and then were exposed to ozone for 60s and this ozonated peroxide mixture was left on the teeth for 20 min. Meanwhile, teeth in group 2 (n=35) were treated with H2O2 38% for 20 min. The L* a* b* and Vita Classic shade values of teeth were evaluated in both groups at base line, after application of H2O2 and ozone in group 1, and after application of H2O2 and then again after another application of ozone in group 2. The statistically significant changes were set at P ≤ 0.05.

RESULTS

Baseline L* a* b* and Vita shade values were comparable between groups (P>0.05). Teeth obtained lighter shades following bleaching with both H2O2 and ozone or with H2O2 alone (P ≤ 0.05). Further bleaching with ozone for teeth already bleached with H2O2 alone showed further improvement of the shades of teeth (P<0.001). Teeth treated with H2O2 and ozone had more shade improvements than those only treated with H2O2 (P<0.001). Also, L* values were increased while b* values were decreased (teeth obtained lighter shades) following bleaching in both groups (P ≤ 0.05). More changes were obtained when both ozone and H2O2 were used (P ≤ 0.05).

CONCLUSIONS

Bleaching with 38% H2O2 and ozone resulted in teeth with lighter shades than bleaching with 38% H2O2 alone.